1. Field of the Invention
The present invention relates to improvements in a heat pump type air conditioner applied to an automotive vehicle.
2. Description of the Prior Art
Various heat pump type air conditioners have been proposed and put into practical use for an automotive vehicle. A typical heat pump type air conditioner is provided with a four-way valve for changing refrigerant flow in heating operation and cooling operation. During the heating operation, an outer heat exchanger functions as a heat absorber, and an inner heat exchanger functions as a heat radiator. On the other hand, during the cooling operation, the outer heat exchanger functions as a heat radiator and the inner heat exchanger functions as a heat absorber. Such a heat pump type air conditioner is disclosed, for example, in Japanese Patent Provisional Publication No. 2-290475 and Japanese Utility Model Provisional Publication No. 2-130808.
As shown in FIG. 11, with the air conditioner disclosed in Japanese Patent Provisional Publication No, 2-290475, during a heating operation, a four-way valve 2 is set as indicated by a continuous line in FIG. 11, and refrigerant is circulated as follows: A compressor 1.fwdarw.the four-way valve 2.fwdarw.a first inner heat exchanger 3.fwdarw.a heating heat exchanger 4.fwdarw.a second inner heat exchanger 5.fwdarw.an expansion valve 6.fwdarw.an outer heat exchanger 7.fwdarw.the four-way valve 2.fwdarw.a receiver 8.fwdarw.the compressor 1. Accordingly, the heat of the refrigerant is transmitted to air led by a blower fan 9 and used for heating a passenger compartment. The heat from an engine 10 is transmitted to the refrigerant through the heating heat exchanger 4 and further transmitted from the refrigerant to air led by a blower fan 11 for heating the passenger compartment. The heat of the air led by a fan 12 is transmitted to the refrigerant through the outer heat exchanger 7.
On the other hand, during the cooling operation, the four-way valve 2 is set as indicated by a broken line in FIG. 12 and refrigerant is circulated as follows: The compressor 1.fwdarw.the outer heat exchanger 7.fwdarw.the expansion valve 6.fwdarw.the second inner heat exchanger 5.fwdarw.the first inner heat exchanger 3.fwdarw.the four-way valve 2.fwdarw.the receiver 8.fwdarw.the compressor 1. Accordingly, the heat of the refrigerant discharged from the compressor 1, is radiated into the atmosphere through the outer heat exchanger 7, and the heat of air led by blower fans 9 and 11 is absorbed into the refrigerant through the first and second inner heat exchanger 3 and 5. Then, the cooled air is supplied into the passenger compartment.
With such a conventional air conditioner, the absorbed heat amount by the outer heat exchanger 7 is decreased during the heating operation under conditions such that the ambient temperature is low, the automotive vehicle is in running, or it is raining or snowing. Furthermore, if the workload of the compressor 1 is constant, the radiated heat amount from the first and second inner heat exchangers 3 and 5, which radiates the sum of the heat absorbing amount from the outer heat exchanger 7, is decreased, and the heating capacity of the air conditioner is lowered. Additionally, the lowering of the heating capacity invites frost to the heat exchanger. This increases the defrost operation and prevents a stable heating operation. Furthermore, since the conventional air conditioner is arranged such that the flow direction of the refrigerant is changed under the cooling and heating operations, it is necessary to change the design of the conduits of the outer and inner heat exchangers 7, 3, and 5 so as to secure durability relative to high temperature and high pressure.
Also, since the conventional air conditioner is arranged to generate heated air by utilizing the waste heat of the engine 10 during the heating operation, it is difficult to sufficiently heat the air if applied to a vehicle which only has a small heat source, such as in a solar car or electric vehicle.